Siding is generally used to cover and protect the exterior walls of a structure or building. Such siding is often made of a weather resistant material such as aluminum or a synthetic material such as a vinyl. The siding is attached to the walls and trimmed at the edges with siding retainer strips. One type of retainer strip used around openings in the wall, such as windows and doors, is generally known as a J-channel due to its cross-sectional shape.
J-channel has a wide base portion which forms a strip that attaches to the wall adjacent a side of an opening in the wall. An extension portion projects continuously from a longitudinal edge of the base portion perpendicular to the base portion. A facing portion extends continuously from a distal edge of the extension portion substantially parallel to the base portion. The facing portion extends back over a fraction of the width of the base portion. These three portions together form a cross-sectional "J" shape and cooperate to form a channel between them.
The retainer strips, such as the J-channel, help hold the siding against the walls and cover the edges of the siding to minimize the amount of wind-blown moisture that may pass behind the siding and damage the walls. Corner pieces have been developed to improve the appearance of the J-channel strips adjacent the corners of rectangular openings where two strips of J-channel meet. Unfortunately, however, the prior art corner pieces permit water which condenses or is blown into the channel formed by the retainer strips to pass behind the corner piece and/or the retainer strips and damage the wall.